Here is a visual of what David was talking about.
This is about a torque free grip as your gonna get and is very repeatable.
what type of grip would your recomend as a replacement
I would try taking the grip off and shooting off the riser first to see how that goes.
Or you could get a set of Johnson grips and put on Scott custom makes his grips to what the customer wants and IMHO they are works of art.
Here are a couple of pics of theside plates he made for my Old Glory.
You can see more info for the grips here
www.johnsongrips.com/ and you can get a hold of Scott here
www.outdoorproshops.com/